The complete and safe closure or filling of the gap space defined between the ground and the tunnel support frames employed during the formation of mining tunnels, underground rooms, roadway tunnels, and the like, is of utmost importance since a complete and proper backfilling of the space defined between the tunnel support frames, with its lagging mats disposed thereon or thereabout, and the ground with backfilling concrete material is not otherwise assured. Insufficient backfilling can of course jeopardize mine safety, in the instance of mine tunnel construction, or the safety of members of the public, other than miners normally employed within mines, which may be using, or within the vicinity of, the other structures which may be constructed due to potentially dangerous cave-in conditions. This is especially true in the instance of construction of tunnels or similar underground structures within ground locations exhibiting low load-bearing capacity.
In order to close the gap space defined between the last tunnel support frame and the ground, it is conventionally known to dispose an end casing within the vicinity of the last tunnel support frame and to connect it, on the ground side, to the last tunnel support frame. However, this operation is expensive, and is additionally difficult to construct or achieve such that a complete and proper backfill will in fact be assured or achieved.
Another type of conventionally known or employed system for closing the gap space defined between the last tunnel support frame and the ground involves the placement of a large-caliber hose upon the tunnel support frame, and the filling of the hose, at a substantially high pressure value, with the backfill concrete. The introduction or employment of the relatively long hose, however, is operationally difficult to achieve, and in addition, auxiliary means must be employed in connection with the hose in order to insure the fact that the hose will remain fixed at its specified location or position while the backfill concrete is being introduced thereinto. Still further, multiple usage of the hose is not possible.